Formaldehyde has been used in the textile industry for a number of years in a variety of applications. Perhaps one of its widest uses is as an ingredient in durable press finishes for fabrics containing cellulosic fibers. Recently, however, there has been increasing concern over safety and health hazards presented by the use of formaldehyde. It has been determined that exposure to formaldehyde on fabrics or in the air can cause allergic reactions in some persons. It has even been suggested that formaldehyde may be a carcinogenic or mutagenic agent.
Because of this concern, efforts are being made in the United States, as well as in foreign countries, to reduce or eliminate formaldehyde usage wherever possible, including textile uses. In the United States, the amount of formaldehyde which can be discharged into waste water streams is limited by governmental regulation, as is the amount of exposure which workers may have to formaldehyde vapors in the air. In Japan, concern over the safety of formaldehyde has led to strict regulations prohibiting any free formaldehyde in apparel for children under two years of age and setting limits on the amount of formaldehyde which may be present in adult apparel. It is anticipated that in the near future, other countries may also enact restrictions or prohibitions on the use of formaldehyde in textile finishing.
Presently, all of the commercial durable press treatments for textile fabrics require formaldehyde or formaldehyde-based compounds. Typically, durable press treatments use methylol derivatives cyclic ureas or methylol carbamates, of which the following are examples: dimethylol ethylene urea (DMEU), ethyl carbamate, and dimethylol dihydroxyethylene urea (DMDHEU). DMDHEU, sometimes called glyoxal resin, is perhaps the most commonly used durable press finishing agent and is formed by reacting urea, formaldehyde and glyoxal. The methylol group (--CH.sub.2 --OH) of all of these durable press agents is formed by formaldehyde and is the group that cross-links with cellulose to give durable press properties. There is no way to prevent some formaldehyde from being released when this cross-linking (curing) occurs. In addition, some free formaldehyde usually remains in the cured fabric. If the residual free formaldehyde is to be removed from the fabric, an after-washing operation is required, but even this is not always totally effective.
Intensive efforts are being made both in the United States and abroad to develop a durable press treatment which eliminates formaldehyde or formaldehyde-based compounds and at least one non-formaldehyde durable press treatment has recently been proposed. Recent U.S. Pat. No. 4,116,625 discloses a non-formaldehyde durable press finish based on imidazoline derivatives combined with acrylic or methacrylic glycidyl containing polymers. It is reported, however, that this process is more expensive and less effective than processes based on formaldehyde, and requires powerful acid catalysts which are of questionable safety.
Therefore, at the present time no commercially acceptable alternatives to formaldehyde-based durable press finishes have been introduced, and formaldehyde is regarded as a "necessary evil" in durable press finishes. The primary approach to the formaldehyde problem has thus been to attempt to reduce formaldehyde levels. Various approaches have been employed, such as varying the catalyst systems used or reducing the amount of formaldehyde-based resin in the finish by employing a resin extender, such as silicone. These approaches are not very effective, however, and the formaldehyde levels in the finishing plant and in the fabric remain undesirably high.